Look at his username and post history. It's no surprise he has vested interest in a "competing" coin. It's about trying to find flaws to discredit Darksend, nothing more. The answer I gave is the most fitting and wasn't provoking either--if you need that level of privacy, you'd make the effort to have received funds from each tx to newly generated addresses before darksending and sending to your final address.
Everything has pros and cons.
Ideally you do NOT want the transaction from the customer to the retailer to be anonymous.From a business point of view, that should be transparent because the block explorer can then serve as an arbitrator of any dispute over remittance of payment. Nor is there any need for it to be anonymous because only the customer and the retailer know the remittence address anyway.
It's what the retailer does with the funds after that that needs to be (and is) anonymous.
It's just like a banking system - if I make a purchase from amazon, I can see the transaction in my bank statement and so can they see it in their statement. But what I can't see is all the other transactions in their account or follow it when they move it.
So Darkcoin has the architecture right for optimally supporting commercial privacy IMO.
...unless of course the business is illegal.